Shock absorber for fluid flow installations



July 25, 1944.

w. R. DAND ET AL SHOCK ABSORBER FOR FLUID FLOW INSTALLATION 2 Sheets-Sheet ,1

Filed April 13, 1942 IIIIIIIIIII Quit! 5 Wm z 5 W. R. DAND ET AL Filed April 13, 1942 2 Sheets-Sheet 2 flilarwys.

. July 25, 1944.

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Patented July 25, 1944 SHOCK ABSORBER FOR FLUID FLOW INSTALLATION S William a. Band, Altadena, and William E. Steen, Pasadena, Calii.'., asslgnors to Smith Meter Company, Los Angeles, Calif., a corporation of California Application April 13, 1942, Serial No. 438,788

3 Claims.

This invention has to do with shock absorbers for fluid flow installations and is more particularly concerned with absorbers of the type employing an expansible, cylindrical sack adapted to absorb the shock incident to surges or sudden shut-offs in flowing fluids.

The device is of use in any situation where it is desirable or necessary to protect valves, flttings, pumps, meters, etc., against the acknowledged harmful efiects of fluid hammer or shock, as well as to accommodate volumetric increases in the fluid which may occur due to temperature changes.

The device is also of the type wherein the cushioning or shock absorbing body of air is positively separated from the flowing fluid, the possibility of entraining the air in the flowing fluid thus being eliminated.

The general objects of the invention are to provide a device which, though of relatively small bulk and light weight, has great shock absorbing efficiency and is capable of responding adequately throughout a wide range of operating conditions; and to maintain this efllciency and capacity over a long period of time even though the operating conditions be extremely severe.

It is a further object to provide a device which may be assembled or disassembled with ease and dispatch and in which there is presented little opportunity for undue wear or for failure, in spite of the fact that certain elements are exposed to conditions which, except for our novel provisions, would bring about early wear or failure.

Other objects and features of the invention will be made apparent from the following detailed description, reference being had to the accompanying drawings, in which:

Fig. 1 is a longitudinal axial section, partly in broken away elevation, showing an embodiment of our invention;

Fig. 1a is a reduced section on line la-la of Fig. 1;

Fig. 2 is an enlarged fragmentary section of a portion of the device appearing at the left end of Fig. 1;

Fig. 3 is a section on line 2-3 of Fig. 2;

Fig. 4 is a section on line 4-4 of Fig. 2;

Fig. 5 is an enlarged fragmentary section of the details enclosed within the area indicated at 5 in Fig. 1, the screen and pneumatic tube being omitted:

Fig. 6 is a section generally similar to Fig. 5 but showing the appearance of this portion of the device prior to certain machining steps;

Fig. 7 is a detached elevation of a cylindrical screen making up a part of the device;

Fig. 8 is a plan view of the screen blank prior to bein fabricated into the form of Fig. '7;

Fig. 9 is an enlarged detail section on line 9-2 of Fig. '7;

Fig. 10 is an enlarged fragmentary section on line Ill-I0 of Fig. '7; and

Fig. 11 is an enlarged fragmentary section on line lI-H of Fig. '7.

Flow line In is connected by flanged T H to the shock absorber which is generally indicated at i2.

Absorber 42 includes a sectional housing ll of generally cylindrical shape but with its ends rounded, section H, which may be considered the body section, and section l5, which may be considered the cap section, being adapted to be disconnectably attached to one another by bolts l6 extending through flanges Ila and Na. To form a fluid tight joint between the sections, an oil resistant gasket l'l, made of neoprene or the like, is compressed between the flanges.

The flanged end of housing section H has a portion l8 which is of greater outsid diameter than is the closed-end portion of that section, the bore I! of portion l8 likewise being greater than is the bore 20 of the closed-end portion 2|. The bore 22 of cap section I5 is of approximately the same diameter as bore 20, and the three bores I9, 20 and 22 are in substantial axial alinement and may be considered as making up the main bore or expansion chamber 22 of the shock absorber.

The connection of T H to absorber l2, or, for that matter, of flow line In to absorber 12, may be any suitable standard type of fitting, but we have here shown a bolted flange connection 24 gasketed at 25, wherein flange 26 is integral with neck 21, the latter, in turn, being integral with housing section I4. Neck bore 22 widens at 22 to open into and to be longitudinally co-ex tensive with enlarged bore l8. Removabl'y mounted within section I and spanning bore l9 and neck bore 29, is screen 22 of which more will be said later. It may be remarked at this point, however, that the bore SI of the screen is of substantially the same diameter as the bores 20 and 22.

It will be seen by reference to Fig, In that section portion l8 and screen 30 define an approximately annular chamber 22 which opens to neck bore 28 through spread opening 29.

Extending through bores 20, 22 and 2| is a pneumatic tube A which is in the form of an elongated cylindrical sack with rounded ends 33 and 34, the ends preferably being of greater thickness than the longitudinally extending wall 34, and being substantially complementary in shape to the rounded ends 35 and 35 of sections l4 and i5, respectively. Tube A is made of a resilient material such as rubber, or, in the event it is to be exposed to oils or gases, of a resilient material'which is oil or gas resistant. For instance, where the absorber is used in connection with petroleum flow lines, the tube may be made of neoprene.

Tube A has an end aperture 31 to receive hollow stem 38 which extends through hollow bosses 39 and 40-(Fig. 2) of housing end 36. The particularities of the stem, its connection of the tube, and its mounting in the housing will be described later. At this point it will suflice to say that the stem. is connected to T 4| whose branches 41a and 4|b mount, respectively, pressure gauge 42 and capped and valved inlet 43. Inlet 43 may carry any suitable check valve 44 such as a conventional Schraeder valve, whereby the air pressure within tube A may be built up or varied to meet varying operating conditions, gauge 42 giving visual indication of the pressure existing within the tube.

Gauge 45 may be connected to annular chamber 32, thus being adapted to give visual indication of the pressure within flow line Ill. The operator, by noting the pressure indicated on gauge 45, may vary the pressure within tube A until gauge 42 shows that the internal pressure has the proper value relative to the external pressure as will give the results which have been found best to suit the indicated external pressure. Then, by varying the internal pressure of the tube, one may vary the resistance of the tube to collapsing pressure by the flow line fluid, and thus regulate the shock absorbing characteristics of the tube best to meet any given flow line condition.

It will be evident that any "hammer" or shock caused by a sudden interruption in the flow of fluid through line ill will be impressed upon and absorbed, at least in the major part, by the air filled flexible tube A; the fittings, piping, and any apparatus in circuit with the flow line thus being relieved of such shock. Likewise, if there be volumetric increase in the fluid of the flow line during non-flow periods, such as may occur due to a rise in temperature, the additional volume is accommodated by compression of tube A.

The screen 30 circumferentially supports tube A whereit spans bore I9 and opening 29, preventing bursting or central deformation of the tube at times when the internal pressure is greater than the external pressure and also serving uniformly to distribute the liquid pressure during instances of surge or shock. The screen perforations permit, of course, the external fluid pressure to be imposed directly on the exterior of tube A. As will be pointed out, the screen may be readily removed to permit cleaning of its perforations, since the latter may become clogged with pipe scale or the like.

Due to the inherent nature of tube A, it is obvious that the walls against which the tube may lie should be as smooth as possible to prevent undue tube-wear, for during periods of operation the housing and tube must, through certain coextensive zones, have relative movement. The screen, of course, forms one such wall and both it and its mounting with the housing must be such as to preserve the specified smoothness. To this in the particular manner illustrated and now to be described. As the screen is to be supported solely at its ends, it is preferable that said ends be annularly reenforced, and we have provided a particularly efficient type of reenforcement which not only contributes to the simplicity of manufacture, but also insures the preservation of the smoothness qualities spoken of above.

The screen 30 (Fig. 7) is made up of a perforated blank 45 (Fig. 8) the edge 48' of the blank being out through unperforated areas so no jagged ends, such as would exist were the cuts to be made from perforation to perforation, are preend we have fashioned and mounted screen 30 sented. Edge 48' is the only single-thickness edge which, when the screen is finally fabricated, is presented at the inside of the screen. The blank is perforated uniformly throughout, though, for sake of simplicity, in Figs. 7 and 8 only a few of the perforations are shown.

One end of blank 46 is notched at 41 to provide a tab 48, preferably having converging side edges 49. At each side of tab 43 will be an end shoulder 50 which is parallel to tab end 5|. The blank is first folded and crlmped along lines 52 and then refolded along lines 53 ,to give the double folds 54 (Fig. 10) which double folds l4 ultimately become the external reenforcing rings of the screen (Fig. 7). However, the last folding is not flnally crlmped down until the blank is rolled into the cylindrical form of Fig. '7. Tab 44 is brought into overlapping relation with end 54' of blank 43 (Fig. 9) and the corners '55 of the tab are slipped between the body of the blank and. the ends of folds 54 (Figs. 7 and 11). The folds? are then tightly and smoothly crlmped down to, retain the tab corners against subsequent placement. Tab 48 is pressed smoothly against the underlying body portion of the screen and soldered thereto or it may be spot-welded at points 58 to prevent subsequent separation. From this point on, folds 54 will be considered as external reenforcing rings.

This method of fabrication gives a screen which is light in weight and yet amply reenforced at its points of end support, and one which presents a sufficiently smooth interior surface to insure that the tube will not be torn or abraded during pe riods of operation.

The screen bore 3! is, as has been said, of the same internal diameter as bore 22 and is to be axially aligned therewith so there may be no projecting edges at the junction of the screen ends and the housing. To secure and preserve this alinement, housing section I4 is bored true at 53 to take one of the rings 54, the spotting of the holes for flange bolts I 5 being such that it is assured, upon assembly, that bore 58 is coaxial with bore 22. Gasket H has the same inside diameter as screen 30 and bore 22, thus giving a flush juncture between the bores of housing section i5, gasket l1, and screen bore 3|. Gasket li presents an annulus 59 which overlies the end of the associated ring 54.

The annular seat 50 (Fig. 5) for the other end of screen 30 is bored true with respect to bore 58 and in axial alinement therewith. Seat 60 is of a diameter to accommodate the over-all thickness of the screen andring 54. A fabrication problem is involved at this point, for, as said above, the entire bore taking the tube A must be as smooth as possible and, at least, must have no sharp projections. It will be appreciated that vwhile seat 60 may be turned so that it will be in true axial alinement with bore 53, there is little likelihood that seat 60 Will be and bore 20 out of axial alinement there would be resulting eccentricity which would, in effect, throw projecting, 90 shoulders into the bore (one shoulder presented by a portion of the end of the screen and the other presented by the diametrically opposite point of the housing). Such projection would tend rapidly to wear or abrade tube A. To avoid this effect, housing section I4 is cast with an extra. mass of material 6| at the general point of juncture of bores I9 and 20 (Fig. 6). The bore 62 of this built-up 'none, is conical, tapering inwardly toward the open end of the housing section. We have found that an approximately 7 inclination with respect to the longitudinal axis of the housing is suitable for the purpose. After cutting annular face 80 to a depth to take ring 54 and with the casting chucked up as it was in cutting that face, a tapering cut at an angle of approximately 7, but with the taper running in a direction opposite to that of taper 62, is taken at 63. The cut of face 03 will be of a depth such that its point of junction 64 with the 90 shoulder 65 formed when cutting seat 60, will be flush with the inner peripheral face of the screen. The inclined face I will, of course. be in axial alinement with the seat GI and bore 58. Thus, there will be no such eccentricity at the junction between the end of the screen and the housing section as would project shoulders into the tube-taking bore. On the other hand, the included angle between faces 02 and 63 is so great (approximately 166 when the cuts are of the taper indicated above) that the annular projection 61 defined by these faces is relatively blunt and will not represent a hazard to the tube.

The screen is of such length that, when the housing sections are bolted together at It, the screen will be clamped between gasket annulus l9 and shoulder 65, the screen thus being held against both rotation and longitudinal movement with respect to the housing section. On the other hand, the screen may be readily removed for cleaning or'replacement by merely disconnecting the housing sections.

We will now turn to the tube connection and mounting. It is obviously important that the connection between tube stem 3| and housing section It be fluid tight so there may be no escape of flow line fluid from the absorber. It is also important that the tube be held from the rotation within the housing, both for reasons of assembly and for reasons of precaution against relative displacement of a harmful nature during operation of the device. The arrangement we have devised i-ully insures that such will be the case.

Hollow stem 3| has a flat head 68 (Fig. 2) and a threaded portion '9 at opposite sides of neck III. This neck is taken within aperture ll and the tube is tightly clamped between heads ll and washer II, the latter being forced into clamping engagement with the tube by nut 12 threaded on portion 68. Portion 89 is flatted at ll (Figs. 2 and 3) to fit a complementarily flatted aperture 14 in housing boss 3!. Aperture I4 is axially alined with cylindrical counterbore ll (Fig. 2 and 4) in housing boss 40, the counterbore 15 being adapted to take a plurality of compressible washers I6 which fit about the reduceddiameter portion ll of stem 38. Washers I! are preferably made of oil resistant material, such as neoprene. At the other end of reduced dimeter portion I1, is a threaded portion ll adapted to support one end of the relatively thick packing washer II and to hold that washer centered with respect to the stem in spite of the fact that the major portion of the washer is annularly cleared from the reduced diameter portion 11. Threaded portion 18 also takes nut III, while extending beyond the threaded portion. the stem is provided with a pipe thread ii to take T ll.

With stem II clamped to tube A by washer II and head II, the tube and stem are assembled with cap II by thrusting the stem, stripp d of all elements except washer ll and nut 12. through flatted aperture I4 and counterbore ID from the inside of the cap. Washers It are then slipped over the stem and into counterbore II, the several washers being of such aggregate thickness that the outer face of the outermost washer extends beyond cap face 82. Washer I! and nut II are then applied to the stem, the nut being turned up to draw face II of nut 12 (which face may be considered to represent a shoulder on the stem) against cap face 83 and the inner face of washer I! against cap face 82, the washer assembly being longitudinally compressed and radially spread in a manner to make up a fluid tight Joint between the stem and the housing.

During this assembly operation, the flats II and 14 cooperate to hold stem 38 and hence tube A against rotation, so the nut may be threaded fully home without otherwise gripping the stem. Likewise. nut 00 may be tightened up during subsequent operation of the device, if the parts have become accidentally loosened, without having to take the housing apart or without having to remove any or the fittings from the stem. since the.

with tube A and its stem thus assembled with cap section I! and with screen I. inserted properly within housing section it, the free end of the tube is slid through the screen bore into bore II, the housing section flanges are brought against opposite sides of washer I1, and bolts it are taken up to connect the two housing sections in fluid-tight association. T I and its gauge 42 and valved inlet 43 are then coupled as shown, and the device is ready for operation.

It will be seen the structure and assembly is such that minimum wear is imposed upon the tube and there is presented minimum opportunity for failure of any kind during service operations. Should occasion arise for repair or replacement of parts, or for the cleanin of foreign matter from the screen, it will be seen the device may be quickly and easily disassembled to allow for such operations.

While we have shown and described a preferred embodiment of our invention, it will be understood that various changes in design, structure and arrangement may be made without departing from the spirit and scope of the appended claims.

We claim:

1. In a device of the character described, a

Jecting through one wall of the housing to the exterior thereof, the bore of the housing having a portion with enlarged inside diameter, there being a flow line inlet opening radially to the enlarged portion of the housing bore, a cylindrical screen extending across said portion but annularly spaced from the inner face thereof, said tube extending through the screen bore, the inside diameter of the screen being substantially equal to the diameter of the bore of the housing at opposite sides of the enlarged portion, said screen having its ends folded over to provide external reenforcing rings, and said rings being circumferentiallyseated in the housing at opposite sides of said enlarged bore portion and holding the screen axially alined with the housing bore.

2. In a device of the character described, a housin a pneumatic tube within the housing, a hollow inlet stem carried by the tube and projecting through one wall of the housing to the exterior thereof, the bore of the housing having a portion with enlarged inside diameter through which the tube extends and which is adapted to communicate with a flow line, a cylindrical screen extending across said portion but annuiarly nular seat and tapering inwardly from said shoulder, and there being another tapered bore portion in the housing tapering in a direction opposite that of the first mentioned tapered portion and starting at the smaller terminus of said first mentioned tapered portion.

3. In a device of the character described, a housing, a pneumatic tube within the housing, a hollow inlet stem carried by the tube and projecting through one wall of the housing to the exterior thereof, the bore of the housing having a portion with enlarged inside diameter through which the tube extends and which is adapted to communicate with a flow line, a cylindrical screen extending across said portion but annularly spaced from the inner face thereof, said tube extending through the screen bore, axially alined,

annular seats in the housing at opposite ends ofthe enlarged bore portion, the ends of the screen being adapted to be taken one, each, in said I seats, one of said seats being end-defined by an annular shoulder, there being a tapered bore spaced from the inner face thereof, said tube extending through the screen bore, axially alined, annular seats in the housing at opp site ends of the enlarged bore portion, the ends 6! the screen being adapted to be taken, one each, in said seats, one of said seats being end-defined by an annular shoulder, there being a tapered bore portion in the housing and concentric with said one anportion in the housing and concentric with said one annular seat and tapering inwardly from said shoulder, and there being another tapered bore portion in the housing tapering in a direction opposite that of the first mentioned tapered portion and starting at the smaller terminus of said first mentioned tapered portion, the defining walls of the two tapered portions defining between them a blunt projection extending into the housing bore.

WILLIAM R. DAND. WILLIAM E. S'I'EEN. 

